KR100675633B1 - Method of forming spacer and a liquid crystal display device having spacer - Google Patents

Abstract

The present invention relates to a liquid crystal display device for preventing the gravity failure due to the volume expansion of the liquid crystal, a liquid crystal layer formed between the first substrate and the second substrate, the first and second substrate, and the first and second A liquid crystal display device including a plurality of column spacers having different heights while maintaining a cell gap between two substrates is provided.

Description

Spacer formation method and liquid crystal display device with a spacer {METHOD OF FORMING SPACER AND A LIQUID CRYSTAL DISPLAY DEVICE HAVING SPACER}

1 is a cross-sectional view schematically showing a liquid crystal display device.

2 is a cross-sectional view schematically showing a liquid crystal display device according to the present invention.

3 is a schematic cross-sectional view of a liquid crystal display device in which a cell gap of the liquid crystal panel is increased after volume expansion of the liquid crystal.

4 and 5 are views showing a spacer formed on the color filter substrate.

6A and 6B are cross-sectional views illustrating a method of forming a spacer according to the present invention.

*** Explanation of symbols for main parts of drawing ***

101: lower substrate 105: upper substrate

108a, 208a: first column spacer 108b, 208b: second column spacer

118: color filter 121: black matrix

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device capable of preventing gravity failure due to volume expansion of liquid crystals.

Recently, with the development of various portable electronic devices such as mobile phones, PDAs, and notebook computers, there is an increasing demand for flat panel display devices for light and thin applications. Such flat panel displays are being actively researched, such as LCD (Liquid Crystal Display), PDP (Plasma Display Panel), FED (Field Emission Display), VFD (Vacuum Fluorescent Display), but mass production technology, ease of driving means, Liquid crystal display devices (LCDs) are in the spotlight for reasons of implementation.

1 schematically illustrates a cross section of a general liquid crystal display device. As shown in the figure, the liquid crystal display device 1 is composed of a lower substrate 5 and an upper substrate 3 and a liquid crystal layer 7 formed between the lower substrate 5 and the upper substrate 3. . Although the lower substrate 5 is a driving element array substrate, although not shown in the drawing, a plurality of pixels are formed on the lower substrate 5, and each pixel is driven such as a thin film transistor. An element is formed, and the upper substrate 3 is a color filter substrate, and a color filter layer for realizing color is formed. In addition, a pixel electrode and a common electrode are formed on the lower substrate 5 and the upper substrate 3, respectively, and an alignment film for aligning liquid crystal molecules of the liquid crystal layer 7 is coated.

The lower substrate 5 and the upper substrate 3 are bonded by a sealant 8 formed on the outer periphery of the substrate, and have a constant cell gap by a spacer 9 formed between them (the upper substrate and the lower substrate). Keep it. In addition, the liquid crystal layer 7 formed between the substrates 3 and 5 drives the liquid crystal molecules by a driving element formed on the lower substrate 5 to display information by controlling the amount of light passing through the liquid crystal layer. .

The liquid crystal display device configured as described above is formed by a drive element array substrate process of forming a drive element on the lower substrate 5, and the upper substrate 3 is formed by a color filter substrate process of forming a color filter. Thereafter, the liquid crystal display device is completed through a spacer and a sealant forming process.

In the driving device array substrate process, a plurality of gate lines and data lines are formed on the lower substrate 5 to define pixel regions, and the gate lines and the data lines are respectively formed in the pixel regions. After forming the thin film transistor which is the driving element to be connected, the pixel electrode is connected to the thin film transistor to form a pixel electrode for driving the liquid crystal layer as a signal is applied through the thin film transistor.

In addition, the color filter substrate process is performed by forming a black matrix on the upper substrate 3, forming a color filter 2 on the upper substrate, and then forming a common electrode 4.

The spacer may be formed as a ball or a column, and the ball spacer is formed by a scattering method, and the column spacer is formed by depositing or coating an organic polymer material on a substrate, and then selectively It is formed by a photolithography process to remove. However, the scattering method interferes with the alignment of the liquid crystal and lowers the aperture ratio because spacers exist in the pixel region through which light passes. Therefore, in order to improve this, a column spacer is proposed which forms a spacer patterned at a desired position.

In addition, in the case of a large liquid crystal display device having a low cell gap, a column spacer is mainly used. This is because it is difficult to produce a ball spacer with a size of 4 to 5 μm or less and it is difficult to secure uniformity of cell gap when applied to a large area.

The column spacer is coated on the lower substrate or the upper substrate with a predetermined thickness, cured, and formed at an arbitrary position on the substrate by a photoresist process. In this case, the column spacer is positioned in the region where the black matrix is formed and is uniformly formed with the same height.

However, the spacer 8 is pressed by the pressure applied when the upper substrate 3 and the lower substrate 5 are bonded and the pressure applied when vacuum injecting the liquid crystal to reduce the cell gap in the center portion of the liquid crystal panel. In particular, this phenomenon occurs remarkably when a large area liquid crystal display device is manufactured. On the other hand, since the sealant 9 formed at the edge of the liquid crystal panel includes glass fibers to maintain the initial cell gap, the cell gap of the edge region of the liquid crystal panel is relatively larger than that of the center portion.

In this state, if the liquid crystal layer formed inside the liquid crystal panel increases in volume due to temperature rise and the cell gap of the liquid crystal panel becomes larger than the spacers, the liquid crystal is driven to the edge of the liquid crystal panel having a higher cell gap, resulting in poor gravity. . In other words, when the liquid crystal is driven to the edge of the liquid crystal panel, the transmittance of the liquid crystal is changed in this portion, and the screen display characteristics are deteriorated.

Accordingly, the present invention has been made to solve the above problems, and an object of the present invention is to provide a liquid crystal display device that can improve the gravity failure of the liquid crystal panel in response to the volume expansion of the liquid crystal layer.

The present invention for achieving the above object is to maintain the cell gap between the first substrate and the second substrate, the liquid crystal layer formed between the first and second substrate, and the first and second substrate, And a plurality of column spacers having different heights.

In this case, the spacer is composed of a first spacer and a second spacer, the first spacer to maintain the set height of the cell gap, the second spacer to maintain the cell gap between the first and second substrate when the liquid crystal expansion give.

The first substrate includes a gate line and a data line arranged vertically and horizontally to define a plurality of pixels, a thin film transistor formed at an intersection of the gate line and the data line, and a pixel electrode formed at each pixel area. Is formed in a gate line or a data line or an intersection thereof, and is composed of a dot pattern.

The second substrate includes a black matrix arranged vertically and horizontally to define a plurality of pixels, a color filter formed in each pixel region, and a common electrode formed on the color filter. It is formed at the intersection of the black matrix and consists of a dot pattern.

In addition, the spacer is formed of one spacer for each pixel or one for every three pixels, the spacer having a different height is Δ0.1 ~ 0.3 based on the cell gap between the first substrate and the second substrate It has a height difference corresponding to the micrometer range.

In addition, the method of forming a spacer according to the present invention comprises the steps of preparing a substrate, applying a spacer forming film on the substrate, irradiating light to the spacer forming film using a mask, and forming the spacer And developing a film to form a plurality of spacer patterns having different heights. In this case, the mask used is a slit mask or halftone mask that transmits only part of the light.

Generally, the spacer forming material used is a photosensitive organic film, and has negative characteristics. That is, since the region to which light is irradiated has a characteristic of being left without being removed by the developer, when the light is irradiated to the organic layer and the amount of irradiated light is adjusted differently for each position, the thickness of the organic layer according to the exposure amount Is formed differently.

Thus, the present invention takes advantage of this feature of halftone masks to form spacers of different heights. At this time, the height of the spacer is formed differently to solve the gravity failure of the liquid crystal display device. Since the liquid crystal expands in volume over a predetermined temperature (about 50 ° C.), even if an appropriate amount of liquid crystal is injected into the liquid crystal panel at room temperature, the liquid crystal expands and becomes thicker than the original cell gap when the temperature rises. Accordingly, the cell gap of the liquid crystal panel becomes higher than the height of the spacer, and the liquid crystal is oriented in the direction of gravity, causing gravity failure. When the spacer is made in consideration of the expansion of the liquid crystal, the liquid crystal is oriented in the direction of gravity I can prevent it. In other words, the spacer having a height corresponding to the cell gap of the liquid crystal panel at high temperature serves to prevent the liquid crystal from being oriented in the direction of gravity.

Hereinafter, the liquid crystal display device according to the present invention will be described in more detail with reference to the accompanying drawings.

2 and 3 schematically illustrate a cross section of the liquid crystal display device according to the present invention. FIG. 2 shows a liquid crystal panel when the liquid crystal layer is not expanded, and FIG. 3 shows a thick cell gap of the panel due to expansion of the liquid crystal layer. It shows a true liquid crystal panel.

As shown in the figure, the liquid crystal display device 100 according to the present invention is a liquid crystal formed between the first substrate 103 and the second substrate 105 and the first substrate 103 and the second substrate 105. It consists of layer 130. Although not shown in the drawing, the first substrate 103 is a driving element array substrate, and gate lines and data lines defining a plurality of pixels are vertically and horizontally formed on the first substrate 103. In the driving device, a thin film transistor (Thin Film Transistor) is formed. In addition, the first substrate 103 is a color filter substrate, and a color filter layer for real color is formed, and a black matrix is formed to block light leakage to the gate / data line and the thin film transistor. It is. In addition, a pixel electrode and a common electrode are formed on the first substrate 103 and the second substrate 105, respectively, and an alignment layer for aligning liquid crystal molecules of the liquid crystal layer 103 is coated.

The first substrate 103 and the second substrate 105 are bonded by a sealant (not shown) formed on the outer side of the substrate, and a color spacer formed between them (upper substrate and lower substrate); 108 Maintains a constant cell gap. In addition, the liquid crystal layer 103 formed between the substrates 103 and 105 drives the liquid crystal molecules by a driving element formed on the first substrate 105 to display information by controlling the amount of light passing through the liquid crystal layer.

In this case, the column spacer 108 includes a first column spacer 108a and a second column spacer 108b having different heights. The first column spacer 108a maintains the cell gap between the first substrate 103 and the second substrate 105 when the liquid crystal layer 130 does not expand, and the second column spacer 108b increases in temperature. As a result, when the liquid crystal layer 130 is expanded and the cell gap of the liquid crystal panel is larger than the first column spacer 108a, the liquid crystal 130 is maintained by maintaining the cell gap between the first substrate 103 and the second substrate 105. ) To prevent movement to the edges of the panel. In this case, the second column spacer 108b may be formed at the same height as the cell gap when the liquid crystal layer 130 is expanded to effectively improve gravity failure.

Even in the prior art, as mentioned above, when the liquid crystal is formed of a liquid material and has a uniform height, the liquid crystal is heated at a high temperature while the liquid crystal is filled in a larger amount than the amount set inside the liquid crystal panel. Due to the low viscosity, the cell gap is concentrated at the edge of the liquid crystal panel, which is relatively high. Therefore, by forming a column spacer capable of maintaining the cell gap of the panel even after the liquid crystal expansion, it is possible to prevent a defect caused by the liquid crystal is concentrated to the edge of the panel.

The column spacer 108 as described above may be formed on the first substrate 103 or the second substrate 105. When the column spacer 108 is formed on the first substrate 103, an area that does not cover the pixel area, that is, It may be formed in a gate line or a data line or an intersection thereof. In this case, the column spacer may be formed such that one column per pixel or one pixel per three pixels.

In addition, even when the column spacer is formed on the second substrate 105, the column spacer is formed in the black matrix region that does not cover the pixel region. 4 and 5, a color filter is formed in the pixel region defined by the gate line and the data line on the first substrate in the second substrate 105, and the gate line and the data line; The black matrix 121 is formed in an area corresponding to the formation position of the thin film transistor, and the column spacer 108 is formed on the black matrix 121. Since the region in which the black matrix 121 is formed is a region through which light does not actually transmit, forming the column spacer 108 in this region does not affect the aperture ratio characteristic at all.

In addition, as shown in FIG. 4, one column spacer 108 is formed per pixel. Alternatively, as shown in FIG. 5, one may be formed per three pixels, and although not shown in the drawing, one may be formed for every two pixels.

The basic concept of the present invention is to prevent gravity defects by forming different heights of column spacers formed to maintain the cell gap of the liquid crystal panel, and the number of column spacers formed per pixel is not limited in the present invention.

As described above, column spacers having different heights may be formed through two or more photolithography processes, or may be formed through one photolithography process through a diffraction or halftone mask.

6A and 6B illustrate a method of forming a column spacer according to the present invention, and in particular, a cross-sectional view illustrating a method of forming a column spacer using a halftone mask.

First, as shown in FIG. 6A, a substrate 200 on which a column spacer is to be formed is prepared, and then a column spacer forming film 208 ′ is coated on the substrate 200. In this case, the substrate 200 is a substrate formed through a thin film transistor process or a color filter process, and the column spacer forming film 208 'is a photosensitive resin film.

Then, a mask 210 is applied to the column spacer forming film 208 'to irradiate light such as UV (indicated by an image table on the drawing).

In this case, the mask 210 uses a diffraction mask or a half-tone mask. In particular, the diffraction mask has a slit structure in the light transmission region, and the exposure amount irradiated through the slit region is smaller than the perfect transmission region for transmitting all the light. When exposure is performed using a mask provided with a transmission region, the thickness of the photoresist film remaining in the slit region and the thickness of the photoresist film remaining in the complete transmission region are formed differently. That is, in the case of the positive type, the thickness of the photoresist film irradiated with light through the slit region is formed thicker than that of the completely transmissive region, while in the case of the negative type, the thickness of the photoresist film remaining in the complete transmission region is thick.

 At this time, the halftone mask 210 is provided with a first transmission area A1 that transmits only part of the light, a second transmission area A2 that transmits all the light, and a blocking area A3 that blocks all irradiated light. Light passing through the mask 210 is irradiated to the column spacer forming film 208 '.

Subsequently, the column spacer forming film 208 ′ exposed through the halftone mask 210 is developed to form a column spacer only in a region where light is irradiated through the first and second transmission regions A1 and A2. Leaving the membrane 208 ', the remaining regions are removed to form a first column spacer 208a and a second column spacer 208b having different heights, as shown in FIG. 6B. In this case, a first column spacer 208a having a relatively low height is formed in an area formed through the first transmission area A1, and a second column spacer 208b having a relatively high height is formed in the second transmission area A2. Is formed. This is because the column spacer forming film has negative type photosensitive film characteristics, and the negative type is used more than the positive type due to its higher resolution than the positive type. On the other hand, it can also be formed using a positive type, in this case, the halftone mask pattern should be manufactured in reverse. That is, the light must be blocked in the area where the pattern is to be left.

As described above, the present invention provides a method of forming a liquid crystal display device and a spacer capable of preventing gravity defects by forming different heights of column spacers. In particular, the present invention provides a volume expansion of the liquid crystal layer when the cell gap of the panel is larger than the first column spacer due to the volume expansion of the first column spacer and the liquid crystal layer formed inside the liquid crystal panel. Thereafter, by forming a second column spacer capable of maintaining an increased cell gap of the liquid crystal panel, the liquid crystal is prevented from moving and solves the gravity defect.

As described above, according to the present invention, by forming column spacers having different heights so as to cope with the volume expansion of the liquid crystal layer, the image quality of the liquid crystal display device can be improved by improving the gravity failure of the liquid crystal panel caused by the liquid crystal being pulled to one side. Can be improved.

Claims (14)

A first substrate and a second substrate; A liquid crystal layer formed between the first and second substrates; A plurality of first column spacers formed on the first and second substrates at the same height as the cell gap when the liquid crystal layer is not expanded to maintain the cell gap between the first and second substrates when the liquid crystal layer is not expanded; And A plurality of second columns formed between the first substrate and the second substrate at the same height as the cell gap when the liquid crystal layer is expanded, and maintaining the cell gap between the first substrate and the second substrate when the liquid crystal layer is expanded; It comprises a spacer, The height difference between the second column spacer and the first column spacer is in the range of 0.1 ~ 0.3㎛ liquid crystal display device. The liquid crystal display device of claim 1, wherein the column spacer is formed of a dot pattern. The method of claim 1, wherein the first substrate, Gate lines and data lines arranged vertically and horizontally to define a plurality of pixels; A thin film transistor formed at an intersection of the gate line and the data line; And A liquid crystal display device comprising pixel electrodes formed in each pixel region. 4. The liquid crystal display device of claim 3, wherein the first column spacer and the second column spacer are formed in an area where the gate line and the data line cross each other. The method of claim 1, wherein the second substrate, A black matrix arranged vertically and horizontally to define a plurality of pixels; A color filter formed in each pixel region; And And a common electrode formed on the color filter. The liquid crystal display device according to claim 5, wherein the first column spacer and the second column spacer are formed on the black matrix. 7. The liquid crystal display device according to claim 6, wherein the first column spacer and the second column spacer are formed in an intersection area of the black matrix. 8. A liquid crystal display device as claimed in claim 4 or 7, wherein one first column spacer and one second column spacer are formed per pixel. 8. The liquid crystal display device according to claim 4 or 7, wherein the first column spacer and the second column spacer are formed in one of three pixels. delete delete Preparing a substrate including a first region and a second region formed outside the first region; Coating a film for forming a column spacer on the substrate; Irradiating light onto the column spacer forming film using a mask; And And developing the column spacer forming film to form a plurality of first column spacers and a plurality of second column spacers having a height of 0.1 to 0.3 μm higher than the first column spacers on the substrate. The method of claim 12, And the mask is a slit mask. 13. The method of claim 12, wherein the mask is a halftone mask.

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